A Sensor System to Assess the Ocular Digital Massage in an Ophthalmic Anaesthesia Training System

Ophthalmic anesthesia training simulators require the evaluation of the proper procedure of (i) orbital needle block followed by (ii) ocular digital massage (ODM). In this paper, to implement digital massage training, an elastic silicone eye mount that articulates the anatomical features of the eye and allows lateral, axial, and compressive movements is presented. An inbuilt permanent magnet in conjunction with four Hall-sensors enables measurements, not only on the movements of the eyeball during digital compression but enables simultaneous measurement of the applied force on the eyeball. Thus, the evaluation of whether the trainee had performed ocular digital compression correctly is feasible. A virtual instrumentation interface developed, measures both the force applied and the movements of the eyeball and issues appropriate warnings to the trainee as part of the training. In the previously developed camera-based system, erroneous output was observed when the eyeball position changed due to compression. The proposed system is designed such that a weak perspective image projection-based methodology itself is adequate to correct this issue. The proposed technique was experimentally validated through results obtained from a prototype unit built and tested. A worst-case error less than 2.0% in the measurement of lateral and axial movements and less than 0.4% error in the computation of compressive force is achieved.